We lost my brother suddenly, when I was 14. He was misdiagnosed with mono, when he had meningitis. Long story, but I do know what your going through, in a way. I watched my parents go through what you are now, unfortunately experiencing. Tough stuff, indeed.
One of my buddies lost his daughter at 6 to a brain tumour. I was the godfather. I remember what he went through, as well.
Words fail here. Prayers you, your son, and your whole family. Terrible thing to have to experience.
Stay strong. One day at a time...
Pax.